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ISO 3382-3 Analysis


After all measurements have been conducted, and each has been defined with a source-receiver distance and speech/noise scenario, select Open Plan Office Parameters from the Project menu.

IRIS will take a short moment to analyse all measurements in the project.

Open plan office analysis

The Open Plan Office Parameters window has two tabs:

  • PATHS (ISO 3382-3), which is used to define paths and display ISO 3382-3 1 parameters

  • VDI 2569, which is a classification of the paths defined on the PATHS tab.

Open plan office parameters

Add Path

  1. Click ADD PATH to create a new measurement path.


    The name of the path can be edited using the text box.

  2. With the path selected, select the corresponding measurements you wish to include on that path. At least four measurements within 2 to 16 m from the source are required.

It's possible to include measurements outside of the 2 to 16 m range, but these will only be used for calculating the distraction distance and average background noise. They will be ignored for the calculation of D2,S and Lp,A,S,4m.


Out-of-range measurements will be coloured red in the list of measurements.


Any incompatible measurements will be listed but greyed out and cannot be selected. Incompatible may mean:

  • Measurement wasn't recorded
  • Missing speech/noise scenario
  • Missing source-receiver distance
  • ON OFFICE PATH wasn't checked


IRIS will automatically calculate and display ISO 3382-3 1 parameters after a sufficient number of measurements have been added to the path.

Open plan office 3382-3

Spatial Decay Rate

The Spatial Decay chart shows:

  • A-weighted speech level vs distance (diamond markers)

  • Best-fit line of the A-weighted speech level used for determining D2,S and Lp,A,S,4m

  • A-weighted background noise level at each measurement position (circle markers)

The D2,S and Lp,A,S,4m values are displayed above the chart, as well as Lp,A,B, the average A-weighted background noise.

Distraction Distance

The Distraction Distance chart plots:

  • Measured STI with distance

  • Best-fit line of the STI with distance, used for determining rD and rP

  • Horizontal lines at STI 0.5 (for rD) and STI 0.2 (for rP)


If the distraction or privacy distance are outside of the physical range of measured distances, the value displayed above the chart will be coloured red.

Background Noise

The background noise used for STI calculations is the average of all measurements on the path. Lp,A,B gives the average A-weighted background noise level, and the octave band data is shown at the bottom of the window.

It is possible to specify an alternative background noise by checking the box and adjusting the spectrum in octave bands. This will change Lp,A,B, rD and rP. The A-weighted background noise levels of the individual measurement positions plotted on the Spatial Decay chart will not be affected.

STI Implementation

ISO 3382-3 1 does not clearly explain how to calculate STI for distraction distance, so Cabrera et al. investigated this issue in detail 2. Following their guidance, IRIS calculates STI for rD and rP according to IEC 60268-16 Ed. 4 3, using the omnidirectional speech effort of ISO 3382-3, with male weighting and redundancy factors, and with auditory spectral masking disabled.


This means the STI value used in the Open Plan Office Parameters window may vary slightly to the STI values displayed in a speech/noise scenario.


Selecting EXPORT button will export all open plan office parameters (both ISO 3382-3 and VDI 2569) to an XLSX file.

  1. International Standard ISO 3382-3 Ed. 1, Acoustics – Measurement of room acoustic parameters – Part 3: Open plan offices (2012). 

  2. D. Cabrera, M. Yadav, D. Protheroe, Critical methodological assessment of the distraction distance used for evaluating room acoustic quality of open-plan offices, Appl. Acoust. 140 (2018) 132-142. 

  3. International Standard IEC 60268-16 Ed. 4.0, Sound system equipment - Part 16: Objective rating of speech Intelligibility by speech transmission index (2011). 

  4. Verein Deutscher Ingenieure, VDI 2569 Draft, Schallschutz und akustische Gestaltung im Büro (2017).